Brain Function Scan System

ABSTRACT

A portable EEG (electroencephalograph) instrument, especially for use in emergencies and brain assessments in physicians&#39; offices, detects and amplifies brain waves and converts then into digital data for analysis by comparison with data from normal groups. In one embodiment, the EEG electrodes are in a headband which broadcasts the data, by radio or cellular phone, to a local receiver for re-transmission and/or analysis. In another embodiment, the subject is stimulated in two modes, i.e., aural and sensory, at two different frequencies to provide the subject&#39;s EPs (Evoked Potentials), assessing transmission through the brainstem and thalamus.

RELATED APPLICATION

This is a divisional application based on application Ser. No.09/908,456 entitled “Brain Function Scan System,” filed Aug. 7, 1997,now U.S. Pat. No. ______

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention, called a “brain stethoscope”, relates to amedical apparatus and more particularly to a portable EEG(electroencephalograph) device to detect, amplify and analyze brainwaves generated by a human and to transmit the results to a remotereceiver.

2. Related Art

It has become evident that human brain electrical activity is preciselyregulated by a complex brain homeostatic system. Normative values areprecisely predictable and have been found to be independent of ethnicfactors. Characteristic patterns of deviation from such normative valueshave been reported for a wide variety of developmental, neurological andpsychiatric disorders.

At the present time it is difficult for emergency personnel to determineif a subject has suffered injury to the brain or the spinal cord,cerebrovascular obstruction (stroke) or hemorrhage (bleeding). If theseconditions could immediately be identified, patients' lives may be savedthrough rapid and appropriate treatment, usually determined after asubsequent neurological exam. The causes of abnormal behavior such asviolent outbursts are often similarly ambiguous.

It is usual, during a routine medical examination, to evaluate the heartusing an EKG (electrocardiogram) device. Usually, there is no attempt todetermine if the patient has any brain dysfunction or conditions thatmay be discoverable using an EEG (electroencephalograph), as generallysuch devices produce an analog wavy set of waveshape tracings which mustbe interpreted subjectively by skilled electroencephalographers.Consequently, although the patient may be suffering from brain damage ordysfunction, such as a tumor, it is often not detected in the course ofthe medical examination. The absence of information about centralnervous system (CNS) dysfunction often results in suboptimal treatment.

As an example, a patient arrives at a hospital emergency room (ER) withcertain physical symptoms of ischemic stroke, or “brain attack”,resulting from blocked blood flow to the brain. Unless the patient istreated promptly, brain cells in the ischemic region would continue tobe deprived of oxygen, possibly destroying parts of his cognitiveabilities, memory and motor skills and possibly resulting in death. Suchadverse effects of ischemic stroke may be halted by immediate andappropriate treatment, for example, injection of tissue plasminogenactuator (tPA), which dissolves clots. However, tPA treatment of apossible stroke victim may be hazardous to initiate, as his physicalsymptoms may be caused by an intracerebral hemorrhage which can beworsened by dissolving clots. Quantitative analysis of the EEG (QEEG)may provide a rapid and objective diagnosis between these alternatives.

As another example, a person may be in a coma when emergency ambulancepersonnel (EMS) arrive. He should not be moved if he has suffered spinalinjury. But the ambulance personnel cannot determine if he has sufferedspinal injury by simply looking at the comatose patient. Somatosensoryevoked potentials (SEPs) provide assessment of the functional integrityof the spinal cord.

Another example of the need for an objective and immediate brainassessment is in situations where there are a number of injured personswho may require medical attention, some of whom may be in a coma. Forexample, on the battlefield or in the event of a train wreck, it may benecessary to separate comatose patients who are breathing and viable andrequire immediate treatment, from those who are still breathing but arebrain dead. And again, in that situation, it is important to tell if apatient who is comatose but alive has a spinal injury, so that he shouldnot be moved. QEEG, SEPs and brainstem auditory evoked response (BAERs)may provide a rational basis for triage in such situations.

A series of publications and patents in the name of Dr. E. Roy Johnrelate to the field of EEG “neurometrics”, which is quantitativeelectrophysiological measurements (QEEG) evaluated relative to normativedata. Generally, a subject's analog brain waves, at the microvolt level,are amplified, artifacts removed and the amplified brain waves convertedto digital data. That data is then analyzed in a computer system toextract numerical descriptors which are compared to a set of norms(reference values), either the subject's own prior data (initial state)or a group of normal subjects of the same age (population norm). Suchanalyses can quantify the level, if any, of deviation of the activity ofany brain region from the reference values.

A computer system based instrument using those principles is the“Spectrum 32” (Cadwell Instruments, Washington). That instrument islarge, non-portable and relatively expensive (tens of thousands ofdollars). It is generally used by experienced neurologists in aneurology clinic or hospital neurology department. It is not suitablefor use in an ambulance, emergency room or a doctor's office for regularmedical examinations. Some of the aforementioned patents which relate toneurometrics are U.S. Pat. Nos. 4,279,258; 4,846,190; 4,913,160;5,083,571 and 5,287,859, incorporated by reference.

There are a number of patents directed to determine whether a person isalive. For example, Allain U.S. Pat. No. 5,029,590 discloses the use ofa pocket-size monitor for life detection. The Allain patent dealsprimarily with detecting heartbeat via EKG and mentions detecting brainwaves using EEG.

In John U.S. Pat. No. 3,706,308 entitled “Life Detecting MedicalInstrument” a portable device has EKG and EEG monitors, a stimulator forevoked brain responses (Evoked Potential—EP), an average responsecomputer and a visual display. It determines if a patient is legallydead by comparison of the patient's brain waves with predeterminedstandards of brain death and does not use comparisons with normalvalues.

There is an existing need for a portable self-evaluating EEG and EPdevice which can be monitored by a hand-held control distant from thepatient. For example, where an injured person's heartbeat cannot bedetected or he is in a coma, he may be taken to a hospital, which has anEEG device and neurologist to detect and evaluate brain waves and todetermine whether he is alive and whether his brain is injured. However,in some emergencies, medical personnel need to quickly determine if apatient has had a stroke or if the patient is alive but in a coma, ordead, or if a person has suffered spinal injury. A particular difficultyarises when some patients have spinal injury and are unconscious. Inthose cases, it would be difficult for medical personnel to ascertainwho can safely be moved or should not be moved because of spinal injury.Persons with such conditions may die due to the lack of medicalinformation, for example, a non-spinal injury patient may be in a comaand is not properly and timely transported to a hospital, or may becomeparalyzed if moved with unrecognized spinal injury.

In general, there are numerous instances in which the ability to make a“brain scan” by a portable EEG/EP device (“Brain Stethoscope”) could bevaluable in assessing the probability of abnormal brain function rapidlyand automatically.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a portableEEG device which can accurately, reliably, continuously and quicklydetermine if the patient is in a coma, is suffering from concussion oris brain dead; if he is having an ischemic stroke or an intracerebralhemorrhage; if he has a serious spinal injury; and, if his behavior isof concern, whether he has abnormal brain function.

In one embodiment of the present invention, called “Version 1”, intendedespecially for use by emergency personnel and emergency vehicles, inhospital emergency rooms and family physician offices, an EEG device hasa limited number of EEG electrodes and may have an EKG electrode,preferably lead 2, and may receive input from a blood pressure device,such as a finger plethysomometer or blood oxygen or saturation meter.Depending upon the particular application, arrays of 1-16 headelectrodes may be used, as compared to the International 10/20 system of19-21 head electrodes generally used in a conventional BEG instrument.The device is small, preferably hand-held, and relatively simple, easyto use and inexpensive. It includes a software programmed microprocessorhaving a CPU (Central Processor Unit) which performs the followingfunctions: (i) it steps (polls) through the EEG electrodes if more thanone electrode is used, so that each symmetrical pair of electrodes(e.g., P3 & P4) is connected simultaneously (electrode pairs are polledin sequence and the instrument is a two-channel or four-channel device)and evaluates the spontaneous EEG; (ii) it provides a timed sequence ofconcurrent stimulations in one or two sensory modalities (modes) to thepatient, such as an audio tone or click at one repetition rate (F₁) andelectrical shocks to peripheral nerves at a second repetition rate (F₂);(iii) based on the responses to these multimodal stimulations, it teststhe functional state of the spinal cord (SSEP—Somatosensory EvokedResponse) and brain stem (Brain Stem Auditory Evoked Response—BAER); and(iv) it assesses the cardiac rhythm.

Preferably, stimulations are used in two different modes, i.e., auditoryclicks and electric pulses to the skin. The stimuli, althoughconcurrent, are at different prime number frequencies to permitseparation of different EPs and avoid interference. Such concurrentstimulations for EP permit a more rapid, and less costly, examinationand provide the patient's responses more quickly, which is important inemergency situations. Power spectra of spontaneous EEG, waveshapes ofAveraged Evoked Potentials, and extracted measures, such as frequencyspecific power ratios, can be transmitted to a remote receiver. Thelatencies of successive EP peaks of the patient may be compared to thoseof a normal group by use of a normative template.

Preferably, to test for ischemic stroke or intracerebral or subarachnoidhemorrhage, the instrument includes a blood oxygen saturation monitor,using an infra-red or laser source, to alert the user if the patient'sblood in the brain or some brain region is deoxygenated.

Another embodiment, called “Version 2”, is particularly for use in fieldconditions in which an immediate indication of brain damage is desiredfrom a number of persons, some of whom may be unconscious. An adhesivepatch, or headband, is placed on each subject. It contains one, or more,EEG electrodes, an amplifier, and a local radio transmitter. A stimulusdevice may optionally be placed on each subject, such as an audiogenerator in the form of an ear plug, which produces a series of “click”sounds. The subject's brain waves are detected, amplified and modulatethe transmitter's carrier wave. A hand-held radio receiver receives theradio waves, demodulates them and converts them into audio tones. Thereceiver may have an array of LED (Light Emitting Diodes) which blinkdepending on the power and frequency composition of the brain wavesignal. Power ratios in the frequencies of audio or somatosensorystimuli are similarly encoded. With the proper training, brain wavemodulated tone signals can be immediately recognized as being generatedby an intact brain or an injured brain. A physician or medical aide whois properly trained to use the Brain Stethoscope may determine, eitherby reading the LCD screen, listening to the audio tones, or by lookingat the blinking LEDs, whether the patient's brain function is abnormaland may evaluate the functional state of various levels of the patient'snervous system.

Another embodiment, called “Version 3”, uses a headband (or patch) and ahand-held receiver. The headband has 2-16 BEG electrodes, an amplifierfor each electrode, an A/D (Analog/Digital) converter and a local radiotransmitter. The transmitter broadcasts an FM or AM carrier which ismodulated by the digital data, from the A/D converter, representing thesubject's brain waves. The hand-held receiver performs the functions ofanalyzing the brain waves and stimulating the subject. It includes adisplay and a microprocessor board. The type of brain wave analysis andstimulation may be the same in Version 1.

In another embodiment, called “Version 4”, the EEG device has a singleelectrode on a headband or an adhesive patch which is placed on aperson's head to detect brain waves which are amplified and transmittedby a micro-transmitter to a microprocessor within a hand-held receiver.The microprocessor analyzes the power spectrum of the brain waves bycomparison to predetermined norms, or by various ratios of power indifferent frequency bands. Version 4 preferably also includes a secondpatch having an EKG electrode and amplifier. Either or both patches maycarry an A/D converter and microtransmitter, the second patch beingplaced on the skin above the left collarbone.

The hand-held receiver may have LEDs, or a display panel, which displaysthe results of the analysis, or an audio output.

In “Version 5” a single electrode is placed preferably midway betweenthe ears. A patch containing the electrode also has an amplifier, an A/Dconverter, microprocessor and a display. The microprocessor analyzes thedigital data and indicates if the subject's brain waves are normal orabnormal. This Version 5 may be especially applicable in a battlefieldsituation.

The invention may be especially useful in cases of an emergency, forexample, a wartime or peacetime explosion/disaster situation where alarge number of people are injured or dead. The portable EEG deviceanalyzes the power spectrum of brain waves to assist evaluating thedegree of injury. By utilizing the portable EEG device, medicalpersonnel may, for example, quickly divide patients into fourcategories: dead, seriously injured who must be moved to a hospitalimmediately, injured who can be moved to a hospital later, and injured,who should not be moved without special precautions.

One advantage of the portable EEG device is that it allows personnel atthe scene of an emergency to determine almost instantly whether a personis alive but suffering from concussion; is having an ischemic stroke oris suffering intracerebral bleeding; if the person is dead or in coma;whether the patient has brainstem or spinal injury; or if the patientdoes not have a heartbeat. The device may be utilized by medicalpersonnel in the field, ambulance medical personnel, firemen andpolicemen as well as other emergency room personnel, and may berelatively simple to use and low in cost. The instrument, when used inemergency vehicles, such as firetrucks and ambulances, preferably has abuilt-in cellular telephone which automatically dials-up or otherwisetransmits its data to a neurometric computer, for example, at ahospital. Thus, while providing immediate automatic evaluation ofpatient's brain state at the emergency site, it can transmit a series ofbrain measurements which are continuously updated to construct a “statetrajectory” for remote evaluation by qualified specialists.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block electronic schematic drawing of the system of thefirst embodiment;

FIG. 2 is a view of the headband and hand-held instrument of the secondembodiment of FIG. 2;

FIG. 3 is a block electronic schematic drawing of the system of thethird embodiment;

FIG. 4 is a chart showing the timing of two stimulations, namely,auditory clicks and somatosensory skin voltage pulses, which aresimultaneous and out-of-phase;

FIG. 5 is a block electronic schematic drawing of the system of thefourth embodiment; and

FIG. 6 is a block electronic schematic drawing of the entire instrument,including the computer analyzer and display, in a patch or headband; and

FIGS. 7, 8 and 9 are top plan views of alternative displays for theinstruments of FIG. 1, 2, 3, 5 or 6.

DETAILED DESCRIPTION Version 1

In the first embodiment, shown in FIG. 1, the instrument 1 is a smalland inexpensive device which is portable and may be hand-held. It uses acomputer system based on a conventional microprocessor, such as an IntelPentium I™ and has a limited internal memory, for example, 100 MB.

The instrument 1 has 1-24 EEG amplifiers, each of which may be connectedto a removable EEG electrode shown as electrodes 10 a-10 p. A suitableelectrode uses an adhesive cover, which is removed before applying it tothe scalp. The electrode may have multiple small barbs, a needleelectrode or a conductive disk, which is removably attached to and maypenetrate the patient's skin; the electrode may also use conductive gel,providing rapid attachment and acceptably low impedance, and may besterile and disposable. In this, and other embodiments, a self-adheringelectrode may be used, for example, the “ZIP-PREP”™ electrode havingstainless steel micro-barbs in an adhesive gel patch, the patch beingapplied with finger pressure.

As shown in FIG. 1, each of the electrodes 10 a-10 p is connected to alead 11 a-11 p which is connected, within the instrument casing 13, to alow-noise programmable multiplexer or electronic switch 15. Theprogrammable switch 15 may have multiple input lines and one or moreoutput lines and is controlled by the microprocessor (CPU) board 42.

The output lines of switch 15 are connected, to a one-, two- orfour-channel low noise preamplifier 12 and to a one-, two- orfour-channel amplifier 14. The amplifier 14 is connected to ananalog-to-digital converter (A/D) and multiplexer within General PurposeInput Board 43 (GPIB).

Preferably the electrodes are in a stretch hat, elastic flexible band orhelmet. The number N of electrodes is generally greater than the numberof amplification channels. However, with micro-miniaturization andreduction in cost of amplification channels, each electrode may beconnected to its own amplification channel. As many as, but not limitedto, 24 electrodes, or as few as one, may be used and as few as oneamplification channel, or as many as N, may be used.

The computer system 40 includes a GPIB (General Purpose Input Board) 15and a microprocessor board 42. The CPIB includes an analog-digitalconverter (A/D) and multiplexer 43. The computer memory 41 contains anormative or reference EEG and EP database 44. Results stored in thecomputer memory or other storage means can be transmitted as a digitalsignal by telephonic or radio transmitter 45 to a remote receiver 46,and may be encoded as audible or visual signals presented by the display48.

A printer 49 may be used to print out a report on the patient.Preferably the printer is a color printer which is used to generate atopographic “heat scale” color-coded map of the patient's head showing,by its colors, the patient's statistical “normal” and “abnormal”regions.

The analog-to-digital multiplexer (A/D multiplexer) provides a digitaloutput from the analog amplifiers. The A/D multiplexer samples the EEGwaves (outputs of amplifiers) at a rate preferably in the range of 200to 300 times per second (or 5 KHz for BAER+SSEP).

The data from the multiplexer is transmitted to a microprocessor board42. The microprocessor has been programmed by an external softwareprogram means, such as a floppy disk recorder, or other input system,such as read-only memory (ROM). The programmed microprocessor(“firmware”) is programmed to perform the data acquisition and the dataanalysis described below. The keypad 47 is used to enter the patient'sage, name and other information.

The program and its controlled microprocessor condition the inputsignals and insure that they are valid biological signals, includingautomatic artifact rejection, and periodic automatic calibration testingand impedance measurements.

The patient is stimulated by the stimulator 16 under control of themicroprocessor board 42 of computer system 40. The stimulator 16 may bea lamp 17A which is flashed. In addition, or alternatively, otherstimulus devices, such as headphones 17B for auditory stimulation andvibratory device 17C or low level voltage electrical skin stimulationdevices may be used.

The computer system 40 automatically provides a timed set of stimuli ofvarious modalities for the stimulator. Stimuli may be deliveredseparately in each modality or concurrently but at frequencies F_(i)which are prime numbers which share no common harmonic (see FIG. 4). Thepatient's brain waves will respond to each stimulus with a component atfrequency F_(i) in the EEG power spectrum, providing an “EvokedPotential” (EP). Those brain waves may be averaged, time locked tostimuli onsets to improve the signal/noise ratio, providing an “AverageEvoked Response” (AER) Filtering and splitting algorithms may reduce lowfrequency noise and remove artifact contaminated samples prior toaveraging.

The AER is the sum of N samples time locked to the onset of stimulidivided by the number of samples, to provide an updated average. N willvary depending upon the usual signal to noise ratio in each sensorymodality. The AER's are held in computer memory 41.

Alternatively, narrow band FFT may be used to compare the power in theEEG at frequencies F_(i) when the stimulator is on vs. off, using anF-ratio.

The device described herein is capable of evaluating both thespontaneous electrical activity of the resting brain (EEG) and theprocessing of unimodal or multimodal sensory information afterstimulation (EPs).

The switch system 15 is controlled over line 18 by microprocessor board42. It switches the electrodes 10 a-10 p to the preamplifiers 12. Forexample, if 3 preamplifiers are used, one is used for common referencefiducial (vertex lead), such as position C_(z) and the other twochannels are automatically switched, by the microprocessor 42, betweenselected electrodes. In this way, one amplifier compresses severalchannels.

Each of the preamplifiers has an input isolation circuit to protectagainst current leakage, such as a photo-diode light-emitting diode(LED) isolation coupler. The preamplifiers are protected from electricalinterference by a radio-frequency filter and a 60-cycle notch filter.Preferably each preamplifier has a computer-controlled switchablefrequency range of 0.5 to 100 Hz, gain of 10,000, or of 100 Hz-5 KHzwith gain of 100,000, common mode rejection of 106 dB, and noise of lessthan 1 microvolt.

EEG recordings may be contaminated by voltages arising from bodymovements, eye motion or other causes. These artifacts, it is assumed,based on prior studies, generate voltages larger than the brain wavevoltage. An updating voltage threshold is computed continuously for eachEEG channel, separately, by calculating the root mean squared (rms)voltage, for example, for a sliding 20-second window and multiplying itby an appropriate constant (rms voltage is approximately 0.2 standarddeviations of amplitude). Segments containing voltages larger than thisupdated threshold are rejected, unless this option is turned off or thecriteria altered by attending personnel. Sampling is suspended after thethreshold is exceeded, for example, for one second, to avoid increasingthe threshold by incorporating the artifact. It is then resumed.Preferably, those intervals (recording periods on each EEG channel) arerejected in which the voltage (signal) exceeds a multiple of the rmsvoltage equal to 6 times (6×) the standard deviation of amplitude.Alternatively, an absolute maximum voltage threshold may be installed.This voltage threshold method provides segments of relativelyartifact-free EEG data. The computer system, in effect, stitches theseintervals together to form a continuous artifact-free EEG sample, whichis recorded in the computer memory.

Because critical decisions may depend upon the accuracy of the BrainStethoscope evaluation, ideally odd and even “split half” samples may beconstructed by assigning intervals to alternately interloaded butindependent samples. For example, the samples from each electrode leadare 2.5 seconds long, the first sample is even-numbered, the secondsample is odd-numbered, etc. Then the odd-numbered samples andeven-numbered samples are individually compared with the norms. If atrue dysfunction exists the measures revealing it must be reliablyreplicable. An abnormality is defined with significance of P<0.05, forexample, “Abnormal” is defined as deviant from normal at the 0.05 level.For example, a “split-half” consists of the first (odd) P1 and second(even) P2 samples. To be “abnormal” the same variable, at the sameelectrode, must be abnormal (at the 0.05 level) in both split-halfsamples. The probability that this could occur by chance is P1×P2(0.05×0.05) or 0.0025. Results from the two split halves may be combinedfor display, with replicated significant results highlighted.

In addition, and optionally, the instrument may have sensors todetermine the heartbeat rate, the blood pressure and the blood oxygenlevel of the subject. As shown in FIG. 1, one or more EKG electrodes 30are connected to an EKG amplifier 31, with a bandwidth from 0.5 to 5000Hz and a gain of 1000, which is connected to an input board 15. Asexplained below, the heartbeat QRS peaks and the R-R intervals aredetected and displayed. A blood pressure (BP) sensor 32 is connected toBP meter (amplifier) 33, which is connected to input board 15.Preferably the BP sensor 32 is a finger tip blood pressureplethysmometer (plethysmograph). An oxygen analyzer 34 (O₂ ANAL), whichis an optional device, is connected to input board 15. A suitable oxygenanalyzer (blood oxygen saturation monitor) uses an infra-red or lasersource to measure oxygen in the blood in body tissues or the brain. Forexample, the INVOS cerebral oximeter is available from Somanetics Corp.,Troy, Mich.

The Brain Stethoscope of Version 1 can be used in three different modes.Mode 1 is concerned with evaluation of a patient who has possiblysuffered traumatic brain/spinal cord injury. Mode 2 is concerned withevaluation of a patient at risk for ischemic stroke (infarct) as againstintracerebral hemorrhage. Mode 3 is concerned with the evaluation ofoverall brain state in patients at risk for a variety of braindysfunctions, ranging from substance abuse to attention deficit todepression to dementia to psychosis. The same basic hardware andartifact rejection, data acquisition and analysis software in the BrainStethoscope is used in all three modes of application, but differentlead configurations are required and different software programs areactivated in the microprocessor, depending on which application isrequired.

Mode 1: In evaluation of traumatic brain/spinal cord injury, only threeelectrodes are required: one electrode on the vertex (Cz) one on themastoid (left or right) and one on the forehead as ground. One channelof amplification will suffice, with a bandwidth of 0.5 Hz to 5 KHz,recording Cz versus the mastoid reference. The amplifier output is splitinto a low-pass EEG channel (0.5 Hz to 70 Hz) and a high pass (100 Hz to1500 Hz) brainstem evoked response channel. The A/D sampling rate shouldbe commensurate with these bandwidths. Auditory clicks, for example, atF1, (40/sec) and 90 dB should be delivered binaurally via stereophonicearphones for 30 seconds every minute. Electrical constant currentshocks, for example, at F2, (27/sec), 0.5 mS, 20 mA, should be deliveredto the fingertip of the right index finger or big toe by an electrodepair imbedded in a finger or toe cot, for the 30 seconds every minutewhen auditory clicks are not being delivered. Preferably a secondchannel is added for EKG (Lead 2), finger blood pressureplethysmomometer, or pulse oximeter, and switched between these inputsto provide information about heart rate, blood pressure and oxygensaturation which is useful to assess shock.Analysis of Mode 1 Data: The EEG recordings obtained during theevaluation period should be analyzed using very narrow band FFT (PastFourier Transform) in narrow, for example, 0.5 Hz increments (steps)from 0.5 Hz to 50 Hz. The power in the low delta (0.5-1.5 Hz), delta(1.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5 Hz), beta (12.5-20 Hz)and high beta (25-50 Hz) frequency bands should be computed andexpressed as absolute (μV²) and relative power (% of power from 1.5 to20 Hz). EEG segments in which low delta power exceeds 2 times deltapower or high beta power exceeds 2 times beta (absolute power) arerejected as contaminated by eye or muscle movements. The approximate ageof the patient should be entered via the keypad 47 of the device. Usingage-regression equations or normal mean values stored in a table in thenormative database 44 (stored in ROM of the microprocessor), the Z scoreof each of the four bands should be computed, where Z=[N−P]/6 andN=normative mean value for a healthy population the same age as thepatient, P=mean value computed from patient data and 6=standarddeviation of the normal population values. For traumatic brain injury,positive Z-scores are expected for the delta and theta bands. Thesevalues are displayed on the screen of display 48 and transmitted to thereceiving station 46 and tracked by a frequently updated (1/minute)trajectory. Increasing Z-scores for delta and/or theta suggestincreasing intracranial pressure from edema or intracranial hemorrhageand may require neurosurgical intervention. For ischemia, positiveZ-scores are expected in the theta band.

Using very narrow band (VNB) FFT, the power at F1 and F2 is computedevery 10 seconds, averaged separately for the 30-second alternatingperiods of auditory click stimulation at frequency F1 and electric shockstimulation at frequency F2. Preferably the (VNB) FFT is computed atincrements (steps) in the range 0.05-0.2 Hz and most preferably at 0.1Hz ( 1/10 sec. sample). Taking advantage of the fact that EEG power at agiven frequency equals the variance at that frequency, the ratios ofpower responsive to auditory stimulation F1 (on/off) and somatosensorystimulation F2 (off/on) are calculated. Alternatively, auditory stimuliat F1 and tactile stimuli at F2 are continuous, providing a steady stateresponse. 10-second samples of EEG are collected, FFT computed at 0.1 Hzincrements and an average of N samples of the FFT is computed. The powerin the F₁ and F₂ windows (Fstim) and the average power in the windows,for example, 40 bins (B) above and below each of the stimulationfrequencies, Fav, is used to compute the value of

$B = {\frac{{Power}\mspace{14mu} {Fstim}}{{Power}\mspace{14mu} {Fav}}.}$

This latter method may be more rapid and sensitive. These ratios,treated as F-values, permit statistical assessment of the probabilitythat the auditory stimuli are traversing the brainstem and thesomatosensory stimuli are traversing the spinal cord and brainstem toreach the cerebral cortex. In addition, using trigger pulses at the F1and F2 frequencies, the microprocessor computes the averaged brainstemauditory evoked responses (BAER) and somatosensory evoked responses(SSER). The averaged BAER and SSER waveshapes, together with the fullpower spectrum, encoded delta, theta, alpha and beta Z-scores and theF-values for the F1 and P2 power in the EEG, are all transmitted to aremote receiving station 46 for updating a display (compressed spectraland EP waveshape arrays and feature trajectories) and for evaluationrelative to normative templates (comparison with normal groups).

For analysis of EKG, QRS peak would be detected and R-R intervalcalculated for heart rate, displayed on an LCD, shown in FIG. 7, asBEATS/MIN.

Mode 2: The detection of ischemic stroke or intracerebral hemorrhage(bleed) is based upon the basic EEG signs of such cerebrovascularevents, arising from the breakage or blockage of a blood vessel. Suchevents are usually on one side of the brain and give rise to asymmetryin slow brain waves. The electrodes are arranged in symmetrical(homologous) pairs, one electrode of each pair being on the left side ofthe head and the other electrode being on the right side of the head. Inthe absence of ischemic stroke, generally the slow waves from bothelectrodes are equal in amplitude and in phase, i.e., symmetric andsynchronous. In this mode, pairs of homologous (L/R) electrodes arepolled, preferably in sequence starting from the front (frontal,temporal, central, parietal, occipital). If any electrode pair showsconsistently asymmetric slow waves, especially in the theta band, it isa sign of possible cerebral ischemia. Using increments of 2.5 secondartifact-free EEG segments, a sliding window 20 seconds wide isconstructed and the average Z-scores of delta, theta, alpha, betaabsolute power and relative power and their asymmetries are calculatedacross the segments within this window. Split-half replication betweensamples constructed from alternate odd and even segments may be used tovalidate results by replication, as described for Mode 1. Thesesequential Z-scores and their Left/Right ratios (asymmetries) are usedto construct a state trajectory for each region (electrode). If the slowwave asymmetry rapidly asymptotes to an approximately constant value, orif the absolute or relative power Z-score (especially for theta ordelta) in a given region reaches a stable abnormal value (dz/dt>0), thecerebrovascular event is probably occlusion of a vessel (stroke); but ifit continues to exacerbate or spread to adjacent regions (dz/dt 0), itis probably a hemorrhage (bleed) which may require rapid intervention.Once the probability of stroke rather than bleed is established, thepatient should immediately be treated, for example, with tPA. Successfulthrombolytic treatment may restore normal symmetry and Z-values.Mode 3: In order to obtain a comprehensive QEEG evaluation of brainstate, it is advisable to scan the EEG in 8 pairs of homologouselectrode placements (FP1/FP2, F3/F4, C3/C4/, P3/P4, O1/O2, F7/F8,T3/T4, T5/T6). Each pair of electrodes provides a short period sample,for example, 1-10 seconds and preferably segments of about 2.5 seconds(artifact free). A fiducial electrode, preferably the electrode atposition cz is recorded continuously to confirm stationarity during thefull scan. Preferably, linked earlobes (A1+A2) are taken as thereference. The electrodes are scanned in pairs a number of times, forexample, 8-48 times and preferably at least 24 times, and ideally 48times, for a total of 120 seconds/pair. In a two-channel 16-electrodesystem (8 pairs) at 2.5 seconds per segment per pair, each scan takes 20seconds. The scans may be performed by an electronic switch, as shown inFIG. 1. The ideal 48 scans take 960 seconds, or 16 minutes, and theminimum 8 scans required for high reproducibility would take 160seconds. In a four-channel system, the corresponding scan times would be480 seconds and 80 seconds. The trade-off between cost (number ofchannels) and scan time may involve 2, 4, 8 and 16 channel versions ofthe Brain Stethoscope for use in situations where rapidity of Mode 3applications may be important. One additional EEG channel should bededicated to continuous Cz recording.

For each of the 2.5 second segments during the total scan, the values ofthe EEG spectral parameters are computed for Cz, which is recorded inevery scan, and the mean M and standard deviations 6computed across theset of segments in the scan. Any segment for which a parameter of Czexceeds M+2.5 6 should be excluded from the scan. Replication betweenodd and even split half samples may be used to further establishvalidity of abnormal findings, as described for Mode 1. Taking advantageof the demonstrated stationarity of the resting EEG, the digital dataaveraged across the full scan is then compared with norms (populationnorms) to determine if the patient's brain function is normal orabnormal. A composite 16 channel scan is constructed from the multiplepairwise scans. The averaged spectral parameters for each lead andsamples of raw data may be transmitted, by cellular phone or othertransmission means, to a receiving PC terminal in a hospital neurologydepartment or neurological center having a suitable computer for itsanalysis, such as the “Spectrum 32” (Cadwell Instruments) or anycomputer with neurometric capability. Interpolated statisticalprobability maps, color coded for significance using a “heat” scale, maybe constructed at the remote receiver. Alternatively, the instrument 1performs its own basic analysis on pairwise data and constructs thecomposite total scan and may also construct a topographic map, andpreferably provides a simple result, i.e., “normal” or “abnormal”, whichmay be followed by such transmission.

The criteria for “normal” and “abnormal” functions may be a “look-up”table. For example, if the power at any electrode is significantly(Z>=2.0) below the norm, for the age group of the patient, then thepatient is considered “abnormal” and an indication (colored light,digital read-out, buzzer, etc.) will be generated. More specificdiagnostic classifications may require transmission of selected clinicalobservations to a remote center for specialized evaluations.

Further evaluation by the instrument's computer memory may have a set ofdiscriminant functions. Such functions may be empirically derived andinstalled in the instrument. In one embodiment, the discriminantfunctions are held as a set in memory as a band or base number for eachdiagnostic category, see U.S. Pat. No. 5,083,571 at columns 4 and 5. Forexample, in the diagnostic category of ischemic stroke, the groups maybe: normal (no stroke), cerebrovascular compromise (stroke) andintracerebral hemorrhage (bleed).

Version 2

The embodiment of FIGS. 2 and 3 is especially adapted for emergencypersonnel, such as firemen, military medical corpsmen, etc. It has onlyone self-adhering electrode 50, or a few such electrodes in a headband51 or cap. The electrode 50 is connected to a tiny amplifier andradio-transmitter 54. The amplifier includes a pre-amplifier andhigh-gain amplifier 52 whose output after A/D conversion 53 modulatesthe AM transmission of the radio transmitter 54. The entire circuit unit(amplifier and transmitter) is preferably less than 0.25 inches thickand the size of a half-dollar.

The transmitter 54 may be small as it transmits only within a shortrange, for example, 50-300 feet. As shown in FIG. 3, a receiver unit iswithin a casing 60 which may be handheld and includes a radio receiver64 tuned to the transmission frequency of the transmitter 54. The unit60 also includes an amplifier 67 to amplify the demodulated signal andto drive a speaker or earphone (headset) 68. A switch 62 is used to turnthe audio on and off and a dial 61 is used to select the band of brainwave frequencies separated by appropriate filters. Position 61 a of thedial 61 is the entire spectrum (T-Total) and positions 61 b-61 e arerespectively the delta (1.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5Hz) and beta (12.5-20 Hz) bands. Each of these, including the entirespectrum, generates a distinctive warble or series of tones in earphones68. A person who has been trained can tell, by the intensity of thesequence of such tones, if the subject's brain waves sound normal orabnormal. Split half replication as in Version 1 may be used andsignificant abnormalities identified by a beep or other appropriatesignal.

Version 3

As shown in FIG. 3, a rapid diagnosis may be obtained by using ahand-held QEEG device.

In Version 3 a headband 90 is applied to a subject. The headband 90includes a self-attaching electrode set 50, preferably 3-16 electrodes,a pre-amplifier for each electrode, and an amplifier 52 for eachpre-amplifier, an A/D converter 53, a micro-transmitter 54 (localbattery operated radio transmitters). For example, in a war timebattlefield situation the patches 90 may be applied to several (3-6)wounded soldiers within 50-100 feet of a blast site. An ear plug 91 isthen inserted into the ear of each subject. The ear plug 91 may be aradio receiver activated by stimulator 72 or, alternatively, itself-generates a sound (click sound) at a selected frequency (F1), forexample, at 40 clicks per second.

A patch 93 containing a self-attaching EKG electrode 94, A/D converter95 and micro-transmitter 96 is placed on the subject's skin above theleft collarbone. The amplified and digitized EKG heart waves aretransmitted by the local radio transmitter 54 to the hand-held device60.

The patient is preferably stimulated by audio clicks and vibratory orelectrical voltage pulses to the skin to provide EPs by the stimulator72 which is controlled by the microprocessor board 73. One of theelectrodes is connected to the vertex as a reference (C_(z) in 10/20system). Preferably, to save time, the stimulations are givenconcurrently, at different frequencies and phase, as shown in FIG. 4.For example, a conductive bracelet or ring is adhered to the subject'sskin and brief low voltage electrical pulses are transmitted to it.These provide a tingling sensation (somatosensory mode) at frequency F1.An earphone plug 91, which is a radio receiver, is inserted into thesubject's ear and click sounds (auditory mode) are transmitted to theearphone at a different frequency F2, where F1 and F2 are differentprime numbers.

The brain waves at the vertex, in a normal brain, will reflect both theF1 and F2 frequencies. The receiver unit 60, as in the first embodiment(Version 1) produces a Fast Fourier Transform (FFT) of the digital data,based on multiple 2.5 second segments. Separate FFTs are generated forthe F1 and F2 frequencies, and their harmonics.

An “F ratio” is derived at each of the 4 frequency bands (alpha, beta,delta, theta). The F ratio is the ratio of power, Pstim, (mean squared)under stimulation, derived from a narrow band FFT, to a norm (thesubject's power, Pref, at that frequency prior to stimulation, e.g., aself-norm). That F ratio may be tracked to determine if there are anychanges in the subject's condition. Alternatively, the F ratio may bebased on a comparison of the subject's brain waves to a normal group(population norm).

When time and the situation permit, split half replication may beoptionally used to validate estimates of abnormality.

An F ratio may be determined in the different ways, as explained abovein connection with Version 1. The F ratio is determined for both the F1and F2 stimulation modes at each of the frequency bands. A trajectory isconstructed using a sequence of measurements. If the subject is stable,those F ratios would stay the same and the first derivative of thetrajectory would approach zero. The power generated at F1 and F2includes their harmonics (preferably five harmonics).

An LCD display 69 (FIG. 7 or 9) provides a visual indication of thepatient's brain state in each frequency band, relative to normal values,by statistical assessment. The cortical response to auditory stimuli (atF1) and somatosensory stimuli (at F2) is similarly encoded in audio orvisual output.

In addition, the receiver unit 60 has a row display 65 which showsamplitude, preferably a row of LCDS. If the brain wave amplitude (totalor at each frequency band) is non-existent or low, the LCDs willindicate this appropriately. The frequency band to be displayed isselected by dial 61 or it cycles automatically, or all may be displayedas an array.

The FFT provides information in the frequency domain. The subject'sbrain waves are compared to a set of normal power spectra held incomputer memory and generated using the same stimulus conditions. If thesubject's power spectra differ significantly compared to the range ofthe predetermined norms, then an “abnormal” display is generated anddisplayed on alphanumeric display 69.

Version 4

In this embodiment, shown in FIG. 5, a single EEG electrode 105 isapplied to the subject. The electrode is in an adhesive patch 100, about2 cm in diameter, or in a headband. The patch 100 (or headband) alsocontains an amplifier 101 (pre-amplifier and amplifier), a battery, anA/D converter 102 and a micro-transmitter 103 (local radio transmitter).The transmitter 103 locally broadcasts the subject's brain waves asdigital data, the data having modulated an FM or AM carrier at aselected frequency, or as modulations of the carrier by the analog EEG.

For example, the patches 100 may be applied to several (3-6) subjectswithin 50-100 of an emergency site. An ear plug 106 is inserted into theear of each subject. The ear plug self-generates a sound (click sound)at a selected frequency (F1), for example, at 40 clicks per second, andmay be a piezo-electric audio generator.

An adhesive patch 93, containing a self-attaching EKG electrode 94, A/Dconverter 95 and microtransmitter 96, is placed on the subject's skinabove the left collarbone.

The hand-held receiver analyzer 110 includes a radio receiver 111, anamplifier 112, a microprocessor board 113, a dial 114, and a display115, which function the same as the corresponding components in theembodiment of FIG. 3.

The microtransmitters 103 and 96 transmit short-range signals whichprovide the global condition of the subject's cerebral cortex and thebrainstem (as evaluated by narrow band fast Fourier transform of thespontaneous EEG and the EEG activated by stimulation from the audiogenerator plug 106) and the waveshape of the EKG.

Using stored normative data from memory 117, based on age-matched normalcontrols and a baseline period (about 1 minute) of measurement of theinitial state of the subject, the hand-held receiver 110 (BrainStethoscope) will compute visual or auditory statistical evaluations ofthe global state of the subject's cortex and brainstem, based upon thenarrow band FFT, and the R-R interval of the EKG. These quantitativeevaluations (Z-scores relative to population norms) will be presented invisual LED display 115 or as audible signals on earphones 116,separately for each subject. The averaged Brainstem Auditory EvokedResponse can be computed and the Peak I-IV measured to assess brainstemintegrity. An updating trajectory display 115 will present the evolutionof each measure, the slope (first derivative) of which will beautomatically evaluated to assess whether the state is stable, improvingor deteriorating. When time and circumstances permit, split-halfreplication may optionally be used to validate critical findings.Priorities, as to the care of the subjects, can then be assigned in aninformed way.

On the trip to the hospital, in an ambulance, the history and updatingtrajectory, augmented by clinical assessments, would continue to betransmitted by transmitter 121 from the hand-held receiver 110. Samplesof EEG Spectra/BAER/EKG waveshapes could be interrogated by theneurometric computer at the hospital (base station).

Assessment of spinal cord injury can be obtained by using the Brain StemSomatosensory Evoked Potential (BSEP). Acquisition of BSEPs by the BrainStethoscope can be accomplished by placing a rubber “cot” on the big toeof each foot and stimulating (via a stimulator 120), a pair ofelectrodes in the toe “cots” at a rate of about 17/sec (F2)—left toe;and 19/sec for (F3)—right toe. The spectral power at a midline foreheadelectrode, on the subject, at frequencies F2 and F3 will reflect thearrival of information at the cortex via the left and right medicallemniscal pathways. Cortical components and components of the BSEPs, atincreasing latencies from 12 ms to 55 ms after each stimulus, willdiminish and disappear depending upon the extent of spinal trauma.Finger tip electrodes (median nerve) can similarly be used to assess thelevel of injury from the 4th cervical vertebra (C4) and above. This willalso estimate the extent of spinal cord injury and the compressioncaused by intrathecal hemorrhage.

The Brain Stethoscope constructs an “initial state norm” of allextracted EEG/Ep/EKG features during its initial set of measures, andthis reference norm includes the variance of each measure. The statetrajectory which it constructs utilizes the Z-transform (i.e.,Z=[Present state minus initial state]/variance of initial state), or theF-ratio (present power/initial power). An automatic alarm can be set(auditory or visual) to alert attendants if any change in the statetrajectory exceeds 2.56 standard deviation (P 0.01) toward furtherdeterioration. This will provide monitoring of the subject during histransport to the hospital.

Version 5

In Version 5, shown in FIG. 6, the entire Brain Stethoscope is in apatch 150 or headband. Preferably, as in the prior embodiment of FIG. 5,an adhesive patch 150 has a single electrode 151 which preferably isplaced midway between the ears, or less preferably on the forehead.

The patch 150 contains an electrode 151, an amplifier 152 (pre-amplifierand amplifier), battery, A/D converter 153, a microprocessor 154 havinga computer memory 155, and a display 156. The entire patch is preferablyless than 3 cm in diameter. The microprocessor 154 performs the QEEGanalysis, described above, for the receiver of Version 4, and preferablyproduces a simple normal/abnormal result. Split-half replication mayoptionally be used to validate critical results, time permitting. Thatresult is shown in the display 156 which is on the front face of thepatch 150. The display 156 may be a green LED 157 (“normal”) and red LED158 (“abnormal”).

In each of the above-described embodiments a reference lead (referenceelectrode) “REF/LEAD” should be used in addition to the active EEGelectrode(s). Preferably the reference electrode is removably attachedat the earlobe or mastoid (temporal bone behind ear). For example, asmall 1-3 cm diameter adhesive patch containing a reference electrodemay be adhered at the earlobe or mastoid. A wire runs from the referenceelectrode to the amplifier (pre-amplifier) which may be in a patch withthe active electrode.

1-44. (canceled)
 45. A medical system for analyzing brain waves of asubject, comprising: a first active EEG (electroencephalograph)electrode detecting a subject's brain waves; a stimulus generatorproviding to the subject sense stimuli in a plurality of stimulus modesto generate Evoked Potentials (EP); a computer system receiving brainwaves from the first electrode, said computer system comprising a memoryunit to store reference data and a microprocessor configured to performartifact rejection and data analysis of spontaneous EEG data and EPdata; an output coupled to the microprocessor displaying a result ofdata analysis and producing a warning when the result indicates injuryto and dysfunction of one of the subject's spinal cord, brain stem andbrain; and a telemetric transmitter unit transmitting the resultwirelessly to a remote receiving station for display and result storage.46. The medical system of claim 45, further comprising an analogamplification channel connected to the active EEG.
 47. The medicalsystem of claim 45, further comprising an analog-to-digital converterdigitizing the amplified brain waves and supplying the digitized brainwaves to the computer system.
 48. The medical system of claim 45,wherein the data analysis is performed using Fast Fourier Transform(FFT) of narrow frequency bands, calculating power at each frequencyband, and performing statistical evaluation by computing a Z-score,where Z=(N−P)/6, wherein N is a mean value of a normative distribution,P is a current measure from the subject and 6 is a standard deviation ofa control age-matched population.
 49. The medical system of claim 45,wherein the sense stimuli in multiple modalities is delivered atdifferent prime number frequencies Fi to separate the Evoked Potentials.50. The medical system of claim 49, wherein FFT is used to compare apower at Fi when the stimulus generator is powered on to a power at Fiwhen the stimulus generator is powered off to compute an F-ratio foreach frequency Fi, wherein the F-ratio=Pstim/Pref, where Pstim is thepower under stimulation and Pref is the power prior to stimulation. 51.The medical system of claim 45, wherein the microprocessor is furtherconfigured to perform a split-half algorithm to improve signal-to-noiseratio.
 52. The medical system of claim 46, further comprising a headgearon which the first electrode and the analog amplification channel aresituated.
 53. The medical system of claim 45, further comprising asecond active EEG electrode detecting a subject's brain waves, thecomputer system receiving brain waves from the second electrode.
 54. Amedical system to analyze brain waves of a subject at a location remotefrom the subject, comprising: a first active electroencephalograph (EEG)electrode detecting a subject's analog brain waves; an attachmentmechanism removably connecting the first electrode to the subject'shead; a radio transmitter situated on the attachment means, wherein anoutput of the first electrode modulates transmission of the radiotransmitter to generate a brain wave broadcast signal based on thedetected analog brain waves; a remote unit comprising a radio receivertuned to receive the transmitted brain wave broadcast signal; anamplifier situated on the remote unit to amplify the received brain wavebroadcast signal; a selectively adjustable filter situated on the remoteunit and separating one of a band of brain wave frequencies and a groupof frequency bands from a brain wave frequency spectrum represented bythe brain wave broadcast signal; and a sound generator coupled to theamplifier, the sound generator producing one of a sound and a series oftones based on the selected frequency band signal.
 55. The medicalsystem of claim 54, further comprising an analog amplification channelsituated on the attachment mechanism, the analog amplification channelconnecting to the active first electrode.
 56. The medical system ofclaim 54, further comprising an analog-to-digital converter situated onthe attachment mechanism, the analog-to-digital converter digitizing theamplified brain waves.
 57. The medical system of claim 54, wherein theattachment mechanism includes a headgear.
 58. The medical system ofclaim 54, wherein the group of frequency bands includes one of a deltaband, a theta band, an alpha band, a beta band and the entire brain wavefrequency spectrum.
 59. The medical system of claim 54, wherein theattachment mechanism comprises a patch.
 60. The medical system of claim54, wherein the analog amplification channel comprises a pre-amplifierand a high-gain amplifier.
 61. The medical system of claim 54, whereinthe remote unit is a hand-held device.
 62. The medical system of claim54, wherein the sound from the sound generator is transmitted throughone of a speaker and earphones to a trained personnel to indicate theexistence of brain dysfunction.
 63. The medical system of claim 54wherein the remote unit further comprises a stimulus generator providingstimuli to the subject in a plurality of stimulus modes, delivered oneof separately and concurrently, wherein the applied stimulation leads togeneration of Evoked Potentials (EP).
 64. The medical system of claim63, wherein the remote unit further comprises a microprocessor toperform artifact rejection and data analysis of spontaneous EEG data andEP data.
 65. The medical system of claim 63, wherein the remote unitfurther comprises a memory unit to store reference data.
 66. The medicalsystem of claim 54, further comprising a receiver situated on thesubject, wherein the receiver receives stimulus input from a stimulusgenerator.
 67. The medical system of claim 54, wherein the remote unitfurther comprises a transmitter unit wirelessly transmitting a result toa remote receiving station for display and result storage.
 68. Themedical system of claim 54, further comprising an output deviceconnected to the microprocessor, wherein the output device displays aresult for each frequency band selected by a trained personnel todetermine the existence of brain dysfunction.
 69. The medical system ofclaim 68, wherein the output device comprises an LCD display for avisual display of the subject's brain state.
 70. The medical system ofclaim 69, wherein the output device comprises a row of LCD displays todisplay the result for each frequency band simultaneously.
 71. Themedical system of claim 63, wherein the stimuli in multiple modalitiesare delivered at different prime number frequencies Fi to separate theEvoked Potentials.
 72. The medical system of claim 71, wherein FastFourier Transform (FFT) is used to compare a power at Fi when thestimulus generator is powered on to a power at Fi when the stimulusgenerator is powered off, to compute an F-ratio for each frequency Fi,where F-ratio Pstim/Pref, where Pstim is the power under stimulation andPref is the power prior to stimulation.
 73. The medical system of claim72, wherein the F-ratio is computed for each stimulation frequency Fi ateach brain wave frequency band.
 74. A medical method for analyzing brainwaves of a subject, comprising the steps of: removably connecting afirst active FEG (electroencephalograph) electrode to a head of thesubject; detecting the subject's analog brain waves; transferring thebrain waves to a microprocessor for data analysis; selectively filteringone of a band of brain wave frequencies and a group of frequency bandsfrom a brain wave frequency spectrum; the microprocessor processing thebrain waves at each frequency band, and performing statisticalevaluation based on reference data stored in a memory unit operativelycoupled to the microprocessor; and outputting a result from themicroprocessor indicating a brain state of the subject.
 75. The medicalmethod of claim 74, further comprising the steps of: amplifying thedetected brain waves using an analog amplification channel situated onan attachment device connecting the first EEG electrode to the head ofthe subject; digitizing the amplified brain waves; and providing thedigitized brain waves to the microprocessor.
 76. The medical method ofclaim 74, wherein the microprocessor is configured to process the brainwaves using Fast Fourier Transform (FFT) and power spectral densitymeasurement.
 77. The medical method of claim 74, wherein themicroprocessor is configured to perform a split-half algorithm toimprove signal-to-noise ratio.
 78. The medical method of claim 74,further comprising the step of delivering stimuli to the subject in aplurality of modes using a stimulus generator operatively coupled to themicroprocessor, wherein the stimuli are delivered one of separately,concurrently and at different prime number frequencies Fi.
 79. Themedical method of claim 74, wherein the step of transferring thedigitized brain waves to the microprocessor further comprises the stepof modulating the transmission of a radio transmitter situated on theattachment device to generate a brain wave broadcast signal, andtransmitting the brain wave broadcast signal to a remote receiver andamplifier coupled with the microprocessor.
 80. The medical method ofclaim 74, wherein the brain wave broadcast signal received by the remotereceiver and amplifier is used to generate a series of tones indicativeof the subject's brain state.